Quinoxalinyl n{10 -oxide phosphates, methods of preparation and use of same as pesticides

ABSTRACT

WHEREIN R and R1 each are selected from the group consisting of lower alkyl, lower alkoxy, lower alkylthio, phenyl, halosubstituted phenyl, lower alkyl-substituted phenyl, and NR2 groups wherein R2 is hydrogen or lower alkyl; X is sulfur or oxygen; and Y is hydrogen, halogen, lower alkyl or lower alkoxy. Novel quinoxalinyl N4-oxide phosphates together with their preparation and use for controlling insects and arachnids are disclosed. They have the formula:

o m v i United States Patent 13,621,021

72] Inventors ernardM a- 1,686,136 8/1654 Shaw 260/294.8

FOREIGN PATENTS ;'j"''"" 666,596 2/1953 GreatBritain 260/290 [2i] AppLNo. 658,598 Primary Examiner-Nicholas S. Rizzo [22] Filed Aug. 7, 1967 Anomey-Harry H. Kline 4 [45] Patented Nov. 16,1971

73 A AmerloanC anlmldC I mgnee shmfordcinn. ompany ABSTRACT: Novel quinoxalinyl N-oxide phosphates 54 QUINOXALINYL'MQXIDIQ PHOSPHATES,

METHON 0F PREPARATION AND USE OF SAME AS PESTICIDES 6 Claims, No Drawings [52] US. Cl. 260/250, 424/200 [51] Int. (I C07d 51/76 [50] Field of Search 260/250 [56] References Cited UNITED STATES PATENTS v 2,922,79l ll I960 Rockett 260/2948 2.503390 4/ I950 Jelinek V l 6 7 /9 together with their preparation and use for controlling insects and arachnids are disclosed. They have the formula:

6 I ea X R Y il N 0- wherein R and R each are selected from the group consisting of lower alkyl, lower alkoxy, lower alkylthio, phenyl, halo-substituted phenyl, lower alkyl-substituted phenyl. and NR groups wherein R, is hydrogen or lower alkyl; X is sulfur or oxygen; and Y is hydrogen, halogen, lower alkyl or lower alkoxy.

QUINOXALINYL moron nosPHATEs, METHODS OF PREPARATION AND USE OF SAME AS PESTICIDES The present invention relates to novel quinoxalinyl N-oxide phosphates, a process for the preparation thereof, and the use of such compounds for controlling insects and arachnids. More particularly, the invention relates to new quinoxalinyl N-oxide phosphates having the fonnula:

X R Y 104 O-methyl O-ethyl 0-2-quinoxalinyl N-oxide phosphorothioate,

O-methyl 0-2-quinoxalinyl N-oxide phenylphosphonothioate,

N,N-diethyl O-methyl 0-2-quinoxalinyl N-oxide phosphoramidate,

0,0-dimethyl 0-2-quinoxalinyl N-oxide phosphorothioate, 0,0-diethyl O-Z-quinoxalinyl N-oxide phosphorothioate, 0,2-methyl-2-quinoxalinyl N-oxide phosphorothioate,

0,0-dimethyl 0-6-methyl-2-quinoxalinyl -oxide phosphorothioate,

0,0-dimethyl 0-6-chloro-2-quinoxalinyl N-oxide phosphorothioate,

0,0-diethyl 0-8-chloro-2-quinoxalinyl N -oxide phosphorothioate,

and

N,N-dimethyl O-ethyl O-2-quinoxalinyl N -oxide phosphorothioamidate.

Advantageously, the compounds of the invention can be prepared conveniently by a plurality of reactions. These include reacting a 2-nitroaniline of the formula:

wherein Y is hydrogen, halogen, lower alkyl or lower alkoxy, with diketene, preferably in the presence of mercuric acetate or other suitable mercury salts, to yield a nitroacetoacetanilide of the formula:

which, when treated with a strong base, such as potassium or sodium hydroxide, yields a quinoxalinone N-oxide having the Reaction of the latter quinoxalinone N-oxide with a halogenated phosphorylating agent of the formula:

wherein Z is a halogen, yields the quinoxalinyl N-oxide phosphate of the invention represented by the formula:

X R Y 0 {V N M:..U: .1

wherein R, R,, X and Y are defined above.

Graphically, the above overall reactions may be shown as follows:

N01 CH:=C--CH Y -9 NHg NH'CCH|'-CCH| (11) 9 e N0g /N\ Y strong base Y -NH-c-oH,-c-cm o 63 Q R x \g Be X R Y z Y g.

III 1 In the preparation of the nitroacetoacetanilide in step (I) above, it is desirable to disperse the nitroaniline reactant in a solvent, such as acetic acid or acetone, and conduct the reaction with the diketene in the presence of mercuric acetate or other equivalent mercury salts and a ketonic solvent, such as acetone, methyl ethyl ketone or methyl isobutyl ketone. The reaction may be carried out at between about and 100 C., but is preferably held at between about 25 and 60 C. Resultant nitroacetoacetanilide may then be separated from the reaction mixture by any known means, such as filtration or centrifugation, then washed with water and treated with a strong base, such as sodium hydroxide, potassium hydroxide and equivalents thereof, preferably as an aqueous solution. A cyclized product, namely, the quinoxalinone N-oxide is obtained. For cyclization, reaction temperatures are generally carried out at an elevated temperature between about 30C. and 100 C. Treatment of the quinoxalinone N-oxide with a strong base, such as potassium t-butoxide and an organic solvent, such as dimethylsulfoxide or dimethylformamide, followed by phosphorylation at between 0 and 70 C. with a halogenated phosphorylating agent yields the desired quinox-. alinyl N-oxide phosphate or thiophosphate as above defined.

Exemplary nitroanilines employed in step (I) include:

2-nitroaniline,

4-chloro-2-nitroaniline,

2-nitro-p-toluidine,

6-chloro-2-nitroaniline,

4-methoxy-2-nitroaniline,

4-ethoxy-2-nitroaniline, and

4-ethyl-2-nitroaniline.

Illustrative typical phosphorylating compounds employed in step (III) are, for instance:

0,0-dimethyl phosphorochloridothioate,

0,0-diethyl phosphorochloridothioate,

O-methyl-O-ethyl phosphorochloridothioate,

0,0-diisopropyl phosphorobromidothioate,

0,0-di-n-butyl phosphorochloridothioate,

0,0-dimethyl phosphorochloridate,

0,0-diethyl phosphorochloridate,

O-ethyl ethanephosphonochloridothioate,

0-ethyl-N,N-dimethyl phosphoramidochloridothioate,

O-ethyl phenylphosphonochloridothioate,

O-ethyl-Ndsopropyl phosphoramidochloridothioate,

O-ethyl-N-methyl phosphoramidochloridothioate,

S,S-diethyl phosphorochloridotrithioate, and

Diethylphosphinothioyl bromide.

The compounds of the present invention are excellent insecticides and arachnicides. They are applied to either plant foliage or to an area in which plants are grown to protect them against the ravages of a variety of insects and arachnids. Further, they are effective against both the adult and larval stages of insects possessing both systemic activity and a low order of mammalian toxicity as well as nonphytotoxicity at pesticidally effective rates. Advantageously, the compounds of the invention lend themselves to use with LV (e.g., Low

'Volume) and ULV (e.g., Ultra Low Volume) dispersing concentrates, wettable powders, emulsifiable concentrates,

granular fomtulations, and as low volume and ultra low volume concentrates (hereinafter referred to as LV and ULV concentrates, respectively). I

Solid formulations, such as dusts, dust concentrates, and wettable powders are readily prepared by admixing usually about 25percent to 95 percent by weight of the active compound with about to 75 percent by weight of a finely divided carrier, such as attapulgite, kaolin, diatomaceous earth, silica, talc, and the like. A small amount, usually about 0.2 to 2.0 percent, by weight, of a surfactant may also be added, if desired. Wettable powders are made in essentially the samemanner as the solids but usually about 0.2 to 2.0 percent by weight of an emulsifying agent is added to the formulation and the wettable powder is dispersed in water and applied as a liquid spray. Among the emulsifying agents useful in the above preparation are the alkyl and aryl sulfonates, polyoxyalkylenefatty acid esters, and polyglycol ethers. These emulsifying agents may also be used in the preparation of the emulsifiable concentrate formulations. In these formulations the active ingredient is generally dissolved in an organic solvent, such as lower alkanol, benzene, acetone, methyl ethyl ketone, cyclohexanone, or the like, with a small amount of emulsifier added. The concentrate is usually then dispersed in water just prior to application.

For LV and ULV applications, the compound may be directly applied as a technical grade liquid. Alternatively, where the compound is a solid, it is dissolved in a small amount of a relatively nonvolatile solvent having a flash point above about 125 F.; a specific gravity at 60l60 F. exceeding about 0.888; and an evaporation rate not exceeding 25 per- -cent in 6 hours at 25 C. and 48 percent relative humidity,

such as Panasol," and applied as such. Further, malathion, chemically identified as 0,0-dimethyl phosphorodithioate of diethyl mercaptosuccinate, and heavy aromatic solvents having a mixed aniline point of F. or below and aromatic content above 60 percent are excellent solvents or diluents for this purpose. In these LV and ULV applications, the concentrate is applied as a finely divided mist or spray, generally with aerial application equipment.

The invention may be further understood by referring to the examples set forth below, which are to be taken as merely illustrative. They are not intended to be construed as limitative. All parts are by weight unless otherwise stated.

EXAMPLE 1 Preparation of 4-Chloro-2 '-Nitroacetoacetanilide In a suitable reaction vessel 34.5 parts of 4-chloro-2- nitroaniline are suspended in 60 parts (by volume) of glacial acetic acid. 1.3 parts of mercuric acetate and 44 parts (by volume) of a 50 percent solution of diketene in acetone were added and the mixture stirred at 25 C. for 5 minutes. An additional 2 parts of mercuric acetate are then added. The temperature rises to 44 C. after 40 minutes. The mixture is next cooled to 30 C. and then allowed to stand at room temperature for 2 days. parts (by volume) of water are added to the stirred mixture which is allowed to settle. The water is poured off and the residual solids dissolved in methanol and crystallized by the addition of water. The yield is 29.5 parts, equivalent to 57.5 percent of theoretical, having a melting point ofbetween 8 1 and 835 C.

EXAMPLE 2 Repeating the procedure of example 1 in every detail except that 4-chloro-2-nitroaniline is substituted for 2-nitro-ptoluidine in the above example, a 57percent yield of 4- methyl-2'-nitroacet0acetanilide, melting point 99 1 00 C., is obtained. The structure of this product is confirmed by its NMR spectra.

EXAMPLE 3 Substituting 6-chloro-2-nitroaniline for 4-chloro-2- nitroaniline in the procedure of example 1 above, there is obtained a 62- percent yield of 6'-chloro-2-nitroacetoacetanilide, melting point equal to l45-l46 C. The structure is confirmed by NMR spectra.

EXAMPLE 4 Preparation of 6-Methyl-2-Quinoxalinone N-oxide To a suitable reaction vessel are added 8.4 parts of 2'-nitro- 4'-methylacetoacetanilide. The latter is then suspended in 150 parts (by volume) of 18 percent aqueous potassium hydroxide solution. The mixture is next stirred at 55-60 C. for threefourths of an hour, and then heated to 7580 C. for one-half hour. It is then allowed to cool and stand overnight at room temperature. The mixture is extracted with chloroform and the aqueous layer is diluted to 400 parts (by volume) and acidified with dilute hydrochloric acid. A brown precipitate forms and is filtered ofi and washed with dilute sodium bicarbonate solution. It is then dissolved in IN sodium hydroxide and reprecipitated with 1N hydrochloric acid to yield 5.7 parts, equal to 92 percent of theoretical, of a dark brown solid. Recrystallization from acetic acid does not appear to change its infrared spectrum.

EXAMPLE 5 Preparation of 6-chloro-2-quinoxalinone N -oxide The procedure of example 4 is followed in every detail except that 2-nitro-4'-chloroacetoacetanilide is reacted with aqueous sodium hydroxide to yield an 89 percent yield of 6- chloro-2-quinoxalinone N-oxide.

EXAMPLE 6 Repeating the procedure of example 4 in every detail except that 8-chloro-2-quinoxalinone N -oxide having a melting point, of 259260 C. (dec.) in a 75percent yield is obtained employing 6'-chloro-2'-nitroacetoacetanilide in lieu of 2'-nitro-4 -methylacetoacetanilide.

EXAMPLE 7 Preparation of 0,0-Demethyl 0-2-quinoxalinyl N-oxide Phosphorothioate 5.0 parts of quinoxalinone N-oxide are suspended in 75 parts (by volume) of dimethylsulfoxide in a suitable reaction vessel. 3.50 parts of potassium t-butoxide are added to give a dark red solution which is cooled in ice. Next, 5.1 parts of 0.0- dimethyl phosphorochloridothioate are added rapidly. After 1 minute, the solution is neutral in pH. It is poured onto a mixture of ice water and methylene chloride. The organic layer is washed three time with water, dried over magnesium sulfate and then evaporated to yield 5.8 parts of dark red oil. The latter is chromatographed on magnesium silicate to give 3.7 parts of pale red solid. Recrystallization from carbon tetrachloride yields 2.4 parts of pale orange solid, possessing a melting point equal to 9798.5 C., and 0.4 part of pale yellow solid, having a melting point equal to 9899 C.

Analysis (in percent): Calcd. for PN SO.,C H

Calcd: P, 10.83; N, 9.79; S, 11.6; C, 41.9; H, 3.84 Found: P, 10.64; N, 9.53; S, 11,24; C, 41.8; H, 4.09

EXAMPLE 8 Preparation of 0,0-Diethyl 0.2-quinoxalinyl N -oxide Phosphorothioate The procedure of example 7 is repeated in every detail, except that 3.0 parts of quinoxalinone N-oxide, 2.10 parts of potassium t-butoxide, and 3.50 parts of 0,0-diethyl phosphorochloridothioate are employed as reactants. Chromatography on magnesium silicate yields 1.90 parts of an orange solid. Recrystallization from petroleum ether yields 0.2 part of solid, having a melting point equal to 5456 C., and 0.8 part having a melting point of 5255 C.

Analysis (in percent): Calcd. for PN,SO C, H,,,,

Caled: P, 9.87; N, 8,92; 8, 10.2; C, 45.9; H, 4.78 Found: P. 9.67; N, 8.80; S, 10.3; C, 45.1 H, 4.84

EXAMPLE 9 Preparation of 0,0-dirnethyl 0-6-methyl-2-quinoxaliny1 N- oxide Phosphorothioate Repeating the procedure of example 7 in every detail, there is obtained a good yield of the above-named compound having a melting point of 124l25.5 C. by substituting 6-methyl-2- quinoxalinone N-oxide for quinoxalinone N-oxide.

Analysis (in percent): Calcd. for PN,SO C,,H,

Calcd: P, 10.32;N, 9.33; S, 10.78; C, 44.0; H, 4.36 Found: P, 10.15; N, 9.18; S, 10.81;C, 44.1; H, 4.l2

EXAMPLE 10 Preparation of 0,0-diethyl 0-6-ch1oro-2-quinoxalinyl N -oxide Phosphorothioate EXAMPLE 1 1 Preparation of 0,0-diethy1 0-6-methyl -2-quinoxalinyl N- oxide Phosphorothioate Following the procedure of example 7 in every detail, 6- methy1-2-quinoxalinone N"-oxide is reacted with 0.0-diethyl phosphorochloridothioate yielding 0,0-diethy1 0-6-methyl-2- quinoxalinyl N-oxide phosphorothioate whose melting point is equal to 86.5-87.5 C.

Analysis (in percent): Calcd. for PN SO C H Calcd: P, 9,43; N, 8.53; S, 9.77; C, 47,6; H, 5.22 Found: P, 9.54; N, 8.61; S, 10.24; C, 48.5; H, 5.41

EXAMPLE 12 Preparation of 0,0-diethyl 0-8-chloro-2- quinoxalinyl N-oxide Phosphorothioate The reaction of 8-chloro-2-quinoxalinone N-oxide with 0,0-diethy1 phosphorochloridothioate in accordance with the process of example 7 yields the above-named compound having a melting point equal to 102.5104 C.

Analysis (in percent): Calcd. for PN SO ClC H Calcd: P, 8.88; N, 8,03; 8, 9.19;Cl, 10. 17; C, 41.3; H, 4.05 Found: P, 8.81; N, 8.06; S, 9.23; Cl, 10.28; C, 41.4; H, 4.12

EXAMPLE 13 Preparation of Diethyl Z-quinoxalinyl N -oxide Phosphate The above name compound whose melting point is 63.0- 64.5 C. is prepared using the process of example 7 by quinoxalinone N"-oxide with diethyl phosphorochloridate.

Analysis (in percent): Calcd. for PN,O,,C,,H,,,,

Calcd: P, 10.41; N, 9.40; C, 48.3; H, 5.04 Found: P, 10.41; N, 9.39; C, 48.4; H, 5.08

EXAMPLE 14 Preparation of Diisopropyl 2-quinoxalinyl N-oxide Phosphate Following the process of example 13 but substituting 0,0- diisopropyl phosphorochloridate for 0.0-diethyl phosphorochloridate yields the above-named compound whose melting point equals 108.5-1 10 C.

Analysis (in percent); Calcd. for PN,0 .,C H,

Calcd: P, 9.5 l; N, 8.60; C, 51.5; H, 4.30 Found: P, 9.76; N, 8.55; C, 51.6; H, 4.95

EXAMPLE 15 Preparation of 0,0-diisopropyl 0-2- quinoxalinyl N-oxide Phosphorothioate The procedure of example 7 is repeated in every detail except that 0,0-diisopropyl phosphorochloridothioate is employed in place of 0,0-dimethyl phosphorochloridothioate to obtain a good yield of the above-named product whose melting point is 76.5-78.0 C.

Analysis (in percent); Calcd. for PN SO C H Calcd: P, 9.07; N, 8.18; S, 9.36; C, 49.2; H, 5.56 Found: P, 8.97; N, 8.18; S, 9.38; C, 49.3; H, 5.66

percent, and 0.001 percent solutions or suspensions in 65 per- 1 cent acetone/35 percent water. 2-inch fiber pots, each containing a nasturtium plant two inches high and infested with about 150 aphids two days earlier, are sprayed with test solution to give complete coverage of the aphids and the plants. The sprayed plants are laid on their sides on white enamel trays which have had the edges coated with No. 50 SAE oil as a barrier. Mortality estimates are made afier holding for two days at 70 F., and 50 percent R.H.

Southern Armyworm Prodenia Eridania (Cramer) The 0.1 percent and 0.01 percent solutions from the aphid test are also used for this test. Sieva lima bean primary leaves are dipped for three seconds in the test solution and set in a hood on a screen to dry. When dry, each leaf is placed in a 4- inch petri dish which has a moist filter paper in the bottom and 10 third-instar armyworm larvae about three-eighths inch long. The dishes are covered and held at 80 F., and 60 percent R.H. After two days, mortality counts and estimates of the amount of feeding are made. Compounds showing partial kill and/or inhibition of feeding are held an extra day for further observations.

Confused Flour Beetle Tribolium Confusum Jacquelin DuVal Compounds are formulated as 1 percent dusts by mixing 0.1 part of the compound with 9.9 parts of talc, wetting with 5 parts (by volume) of acetone and grinding with a mortar and pestle until dry. One hundred and twenty-five mg. of this 1 percent dust are then blown into the top of a dust settling tower with a short blast of air. The dust is allowed to settle on 4-inch petri dishes for two minutes, giving a deposit of approximately 87 mg./sq. foot of the 1 percent dust. The dishes are removed and 25 adult confused beetles are added immediately. The dishes are held for 3 days at 80 F. and 60 percent R.H. following which mortality counts are made. Large Milkweed Bug Oncopelms Fascialus Dallas The 1 percent dusts described above are used in this test. 25 mg. of the 1 percent dusts are sprinkled evenly over the glass bottom of a 7-inch diameter cage giving a deposit of approximately 94 mg./sq. foot of the 1 percent dust. Water is supplied in a a 2-ounce bottle with a cotton wick, 20 adult bugs are added and a screen cover placed on the top. Mortality counts are made after holding for 3 days at 80 F. and 60 percent R. German Cockroach Blattella germanicd (Linneaus) The procedure is the same as for the large milkweed bug test, except that in this test only adult males are used. Housefly Musca domestica Linnaeus 7 Groups of 25 adult female housefiies are lightly anesthetized with carbon dioxide, place in wide'mouth pint mason jars, and covered with a screen cap. The test compound is fonnulated as an emulsion containing p.p.m. of test material, an emulsifier, acetone, and water. The mouth of the vial is covered with a single layer of cheesecloth, inverted and placed on the screen cap so that the flies can feed on the solution through the screen. Mortality counts are made after 2 days at 80 F. Southern Corn Rootworm Diabrotica undecimpuncrala howardi Barber W The compound in test is formulated as a dust and incorporated into soil at the equivalent of 50 pounds per acre. The soil is subsampled into bottles, and 10 6- to 8-day old rootworm larvae added to each bottle, which is then capped. Mortality counts are made after 6 days at 80 F., percent RH.

The results are presented in tabular form in table 1 below.

TABLE I Southern Southern Benn aphid armyworm corn 'IC, MB. GC. Housefly, rootworrn, Compound 0. 1% 0. 01% 0.001% 0. 1% 0. 01% 1% 1% 60 p.p.m. 50 lbs-[acre S i N O (O C2115)? 0 e 100 100 100 100 100 100 90 100 100 100 it i \N/ -OP 0 (1H,

9 e 100 100 100 100 100 100 l s; CH3

i N OP (O C2115):

0 e 100 100 100 100 100 100 80 100 100 100 he 1 TABLE I Cntir 1u d Southern Southern Bean aphid armyworm 'IC, MB, (3C. Housefly, rootwomi, Compound 0.1% 0. 01% 0. 001% 0.1% 0. 01% 1% 1% 1% 50 p.p.m. 50 lbs.lacro 100 100 100 100 50 100 3s 68 N 1, 0 H3 N O-P(OCH;)5

i N/ O-P (002115):

0 e 100 100 no 0 so 100 so 100 o i 0 P 3E192 Control 1 T9 Triolium con/mum.

2 MB =Millrweed bug.

EXAMPLE 17 The larvicidal activity of illustrative compounds of the invention is shown by the following tests wherein the compounds of the invention are employed against mosquito larvae. The procedure used and results obtained are set forth below in table II.

Common Malaria Mosquito Anopheles quadrimaculatus Say Larvicide Test Groups of 25 larvae of the common malaria mosquito are transferred with a medicine dropper to a 50 ml. beaker containing 25 ml. of water. The test compound is formulated as an emulsion containing test material, an emulsifier, acetone, and

water. This emulsion is diluted with sufficient percent acetone/35 percent water mixture to give 0.4 ppm. of active ingredient in solution when the emulsion and water containing the larvae are admixed. Mortality counts are made after 24 60 S i N O-iMOCsHt):

a G0 German cockroach.

NJ-O-fl' (0 0.1111) The miticidal activity of exemplary compounds of the invention is illustrated by the following test using the twospotted spider mite.

Two-spotted Spider Mite Tetranychus urticae (Koch) Sieva lima bean plants with primary leaves 3 to 4 inches long are infested with about 100 adult mites per leaf 4 hours before use in this test. The mite and egg infested plants are dipped for 3 seconds in the 0.1 percent, 0.0! percent and 0.001 percent solutions used in the armyworm tests, and the plants set in the hood to dry. They are held for 2 days at 80 F., 60 percent R.H., and the adult mite mortality estimated on one leaf under a stereoscopic microscope. The other leaf is left on the plant an additional 5 days and then examined at 10X power to estimate the kill of eggs and of newly hatched nymphs, giving a measure of ovicidal and residual action, respectively.

The results are ummaxiz dintablgllit lcw.

TABLE III Two-spotted spider mites Compound 0.1% 0.01% 0.001%

ll N 0-? (O 023:5):

s l \N/ 202 ea CH /N\ i N/ 0-]? (O C3H5)g i N 0-? (OCHa):

O 0-1 (0 CzHuh 0 0 OCHl a 1):

S o-l to can).

We claim: 1. Acom pound of the forrnula:

wherein R and R are selected from the group consisting of lower alkyl, lower alkoxy, lower alkylthio, phenyl, halophenyl. lower alkylphenyl and NR, groups wherein R is hydrogen, or lower alkyl; X is sulfur or oxygen; and Y is hydrogen, halogen, lower alkyl or lower alkoxy.

2. A compound according to claim 1: 0,0 dimethyl 0-2- quinoxalinyl N-oxide phosphorothioate.

3. A compound according to claim 1: 0,0-diethyl 0-2-quinoxalinyl N-oxide phosphorothioate.

4. A compound according to claim 1: 0,0-dimethyl 0-6- methyl-Z-quinoxalinyl N-oxide phosphorothioate.

5. A compound according to claim 1: 0,0-diethyl 0-6- chloro-2-quinoxalinyl N-0xide phosphorothioate.

6. A compound according to claim 1: diethyl Z-quinoxalinyl N-oxide phosphate.

* l i i 

2. A compound according to claim 1: 0,0-dimethyl 0-2-quinoxalinyl N4-oxide phosphorothioate.
 3. A compound according to claim 1: 0,0-diethyl 0-2-quinoxalinyl N4-oxide phosphorothioate.
 4. A compound according to claim 1: 0,0-dimethyl 0-6-methyl-2-quinoxalinyl N4-oxide phosphorothioate.
 5. A compound according to claim 1: 0,0-diethyl 0-6-chloro-2-quinoxalinyl N4-oxide phosphorothioate.
 6. A compound according to claim 1: diethyl 2-quinoxalinyl N4-oxide phosphate. 